GB2109804A

GB2109804A - Modified polyethylene terephthalate molding material

Info

Publication number: GB2109804A
Application number: GB08225735A
Authority: GB
Inventors: Yuzo Toga; Toshio Shimada; Ichiro Okamoto
Original assignee: Daicel Chemical Industries Ltd
Current assignee: Daicel Corp
Priority date: 1981-09-11
Filing date: 1982-09-09
Publication date: 1983-06-08
Also published as: GB2109804B; US4415727A; JPS5845225A; JPH0346487B2; DE3233653A1

Description

1 GB 2 109 804 A 1

SPECIFICATION Modified polyethylene terephthalate molding material

This invention relates to a modified polyethylene terephthalate molding material. More particularly, it pertains to a polyethylene terephthalate molding material for molding bottles of 5 polyethylene terephthalate which is difficult to crystallize.

BACKGROUND OF THE INVENTION

It is well known that polyethylene terephthalate is one of the most useful synthetic fibers and is widely used as film in industrial uses and for packaging foods. Recently polyethylene terephthalate has come into rapid use in biaxially stretched bottles for packaging liquid foods and cosmetics. This is attributed to the fact that, as compared with polyvinyl chloride or polyolefin-EVA (ethylene-vinyl 10 alcohol) copolymer, double-layered material conventionally used for bottles, polyethylene terephthalate is excellent in hygienic properties, impact resistance, heat resistance, transparency, gas barrier properties, chemical resistance, weatherability, etc., and has well balanced physical properties for bottles.

However, polyethylene terephthalate is essentially a highly crystalline resin and, therefore, appears 15 opaque. Hence, various techniques have been employed to obtain transparent bottles of polyethylene terephthalate.

In general, polyethylene terephthalate bottles (hereinafter abbreviated "PET bottles") are manufactured by blow molding techniques such as direct blow molding, injection blow molding or biaxially stretching blow molding. In order to manufacture transparent PET bottles, it is important, from 20 the viewpoint of material aspects, to select polyethylene terephthalate having a proper molecular weight according to the blow molding method and the section thickness of the molding to be manufactured and, from the viewpoint of molding aspects, it is necessary to preliminarily dry the PET chips well or to rapidly cool the resin in the molten state as fast as possible. In particular, with thick- walled bottles, it is of importance to minimize crystallization of polyethylene terephthalate in the period 25 between parison molding and blow molding.

As one approach for modifying polyethylene terephthalate to satisfy the above requirements, it is known to use a small quantity of isophthalic acid together with terephthalic acid as the dicarboxylic acid component of PET or to use a small quantity of neopentyl-glycol or cyclohexanedimethanol together with ethylene glycol as the glycol component of PET, thus producing copolymeric PET having a slow 30 crystallizing rate by copolymerizing the above-described ingredients (for example, see Lecture Abstracts of the 11 th Colloquium on Structure and Physical Properties of High Polymers, held by the Japanese High Polymer Society, Kanto Branch, on June 16, 198 1, "Recent Progress in Modification of Polymers", p. 3). - With the above situation in mind, the inventors intensively investigated glycols functioning as 35 comonomers which provide a PET crystallization-controlling effect and, as a result, found that 2-methyl 1,3-propanediol is extremely excellent as such a glycol, thus having achieved the present invention.

SUMMARY OF THE INVENTION

The present invention provides a polyethylene terephthalate which is excellent as a material for molding thick-walled PET bottles, which contains terephthalic acid as a major dicarboxylic acid 40 component and ethylene glycol as a major glycol component, and contains 0. 1 to 15 mol%, based on the glycol component, of 2-methyl-1,3-propanediol as part of the glycol component.

DETAILED DESCRIPTION OF THE INVENTION

The amount of ethylene glycol used as a major glycol component is 70 moi% or more, preferably moi% or more, based on the total amount of glycol component present. The amount of terephthalic 45 acid used as a major dicarboxylic acid component is 80 moi% or more, preferably 90 moi% or moe, based on the total amount of the dicarboxylic acid component present.

In general, polycondensation of an alkylene glycol having a methyl side chain with terephthalic acid or a lower alkyl ester thereof (wherein the lower alkyl moiety contains from 1 to 9 carbon atoms) gives a high molecular weight polyester. It is also known that when the methyl group is present in an so asymmetric position of the alkylene glycol, the resulting polymer crystallizes only with difficulty due to irregularity in the polymer structure. As commonly used alkylene glycols having a methyl group in an asymmetric position, there are, for example, 1,2-propylene glycol, 1,3- butylene glycol, etc. However, in these glycols, the carbon atom to which the methyl side chain is bound also has a hydroxy group to form alkylene glycols having a secondary hydroxy group and a primary hydroxy group. Thus, the two hydroxy 55 groups show different reactivity with carboxyl groups of a dicarboxylic acid. Particularly, the reactivity of the secondary hydroxy group is much less than that of the primary hydroxy group and, as a whole, the reaction rate of such a glycol is much slower than that of a glycol where the two hydroxy groups are both primary hydroxy groups.

2-M ethyl- 1 3 -propa nediol used in the present invention has one methyl group as a side chain and 60 has an asymmetric chemical structure. The use of this compound as a component of a polyester 2 GB 2 109 804 A 2 polymer makes the structure of resulting polyester polymer irregular, which extremely reduces crystallinity and the crystallizing rate. In addition, since the two hydroxy groups are primary hydroxy groups, they show high reactivity and easily react with carboxyi groups to form ester bonds.

The amount of 2-methyl-1,3-propanediol to be mixed with ethylene glycol ranges from 0.1 to 15 mol%, preferably 2 to 10 mol%, based on the total amount of glycol component present. The 2m ethyl- 1,3-propanediol reacts with an equal mol of the dicarboxylic acid and, thus, the amount of 2m ethyl- 1,3-propa nediol as described above is the same in the final polyester (i.e., polyethylene terephthalate). If the amount is less than 0.1 mol%, the above-described effects attributable to 2methyl-1,3propanediol are difficult to obtain, whereas if more than 15 mol% is used, the melting point and crystallinity of the resulting polymer is decreased so much that the polyester becomes inferior as a 10 bottle-molding material from the viewpoint of heat resistance and mechanical strength.

The modified polyethylene terephthalate of the present invention can be produced according to known processes for producing copolymerized polyesters as described in, for example, U.S. Patents 2,465,319 and 2,071, 250, i.e., directly reacting a dicarboxyliG acid with a glycol or utilizing an interesterification reaction between a dicarboxylic acid lower alkyl ester and a glycol. The latter process 15 is more specifically described below.

One mol of dimethyl terephthalate and a molar excess, i.e., 1.1 to 2.0 mols (total) of a mixture of ethylene glycol and 2-methyl-1,3-propanedioi at the earlier recited proportions are subjected to interesterification reaction in a nitrogen stream at ordinary pressure at temperature of about 150 to about 2401C using a conventional esterification catalyst, methanol produced is distilled off and, if desired or necessary, a catalyst, a coloration-preventing agent (for example, tridecyl phosphite, etc.), etc., is/are added thereto, followed by conducting polycondensation at about 250 to 3001C under a reduced pressure of up to 5 mm Hg, The thus obtained polymer may be subjected to solid phase polymerization at a temperature 20 to 501C lower than its melting point in vacuo or in a nitrogen stream in order to further increase the molecular weight of the polymer.

As the above esterification catalyst, a wide variety of catalysts can be Lised. For example, there can be illustrated titanium compounds such as tetra methoxytitanium, tetra ethoxytitaniu m, tetra-npropoxytitanium, tetra-iso-propoxytitanium, tetrabutoxytitanium, etc., tin compounds such as di-nbutyltin dilaurate, di-n-butyltin oxide, dibutyltin diacetate, etc. , and a combination of an acetate of magnesium, calcium, zinc or the like and antimony oxide or the above titanium compounds. These catalysts are preferably used in an amount of 0.002 to 0.8 wt% based on the copolymer to be produced.

In addition to the coloration-preventing agent, other conventional additives such as polymerization accelerator, brightening agent, light-resistant agent, etc., may be added according to the end use of the polyester.

The modified polyethylene terephthalate obtained by the process of the present invention is 35 manufactured using terephthalic acid (or a lower alkyl ester thereof wherein the lower alkyl moiety contains from 1 to 9 carbon atoms), ethylene glycol and 2-methyl-1,3- propanediol as starting materials.

As additional copolymerizable components, there may be used polybasic aliphatic carboxylic acids containing from 3 to 30 carbon atoms, such as adipic acid, azelaic acid, sebacic acid, etc., polybasic aromatic carboxylic acids containing from 8 to 30 carbon atoms, such as isophthalic acid, trimellitic 40 acid, pyromellitic acid, 2,6-naphthalenedicarboxylic acid, etc., and polyhydric alcohols containing from 3 to 30 carbon atoms, such as propylene glycol, neopentyl glycol, 1,6- hexamethylene glycol, 1,4 cyclohexanediol, cyclohexanedimethanol, trimethylolpropane, pentaerythritol, etc., in suitable amounts according to the end use of the polyester.

The polyethylene terephthalate obtained by the present invention has an intrinsic viscosity of 0.4 45 or more, preferably 0.4 to 1.2. The modified polyethylene terephthalate obtained by the present invention is suited as a material for molding bottles, particularly thick- walled bottles. Transparent bottles having good appearance can be obtained from the material by any conventional direct blow molding, injection blow molding and biaxially stretching blow molding method.

A The present invention will now be described in more detail by the following examples of preferred 50 embodiments of the present invention which, however, are not to be construed as limiting the present invention in anyway.

Additionally, "parts" in the following examples are parts by weight, and data given in Table 1 are obtained by the following measuring methods.

(1) 2-M ethyl- 1 3-propa nediol Group Content:

Indicated in terms of moN, based on the total glycol groups present, of 2methyi-1,3-propanediol group determined by the NMR analysis (nuclear magnetic resonance) spectrum of the resulting resin.

(2) Intrinsic Viscosity:

Measured at 241'C in o-chlorophenol.

(3) M.P. and Heat of Fusion:

Measured by means of a differential scanning calorimeter, model DSC-1 B, made by the Perkin Elmer Co.

1 3 GB 2 109 804 A EXAMPLE 1

155.4 Parts of dimethyl terephthalate, 73.0 parts of ethylene glycol, 2.2 parts of 2-methyl-1,3- propanediol, and 0. 10 part of a catalyst (tetra butoxytitan iu m) were charged in a reactor equipped with a double helical ribbon type agitating element, and the mixture was heated at 1 801C for one hour under ordinary pressure in a nitrogen stream, then at 2301C for 3 hours to distill off methanol in an amount of 5 89% of the theoretical amount. 0.10 Part of tetrabutoxytitanium and 0.25 part of tridecyl phosphite were further added thereto, and the temperature of the mixture was raised to 2700C. The pressure within the reaction system was reduced to 0.2 mm Hg over 45 minutes, and the system was kept for 4 hours under this condition to react.

EXAMPLES 2,3 AND 4 AND COMPARATIVE EXAMPLES 1 AND 2 Polymerization was conducted under the same conditions as in Example 1 except for charging the compounds in the amounts given in Table 1. The physical properties of each of the resulting polymers are tabulated in Table 1.

TABLE 1

Com- Comparative parative Example Example Example Example Example Example 1 2 3 4 1 2 Charged Amounts Dimethyl terephthalate 155.4 155.4 155.4 155.4 155.4 155.4 (parts) Ethylene glycol (parts) 73.0 71.9 71.1 67.0 74.5 59.6 2-M ethyl- 1 3-propanediol 2.2 3.8 4.9 10.8 0 21.6 (parts) Tridecyl phosphite (part) 0.25 0.25 0.25 0.25 0.25 0.25 Tetrabutoxytitanium (part) 0.20 0.20 0.20 0.20 0.20 0.20 Content of 2-methyl-1,3- 1.9 3.5 4.6 9.8 0 21.4 propanediol group (moN Intrinsic viscosity (di/g) 0.49 0.52 0.48 0.51 0.51 0.52 M.P. (OC) 248 244 238 221 251 Heat of fusion (cal/g) 10.3 9.5 8.9 6.6 10.9 No peaks for fusion were observed on the differential scanning calorimeter.

REFERENCE EXAMPLE 1 Each of the polymers obtained in Comparative Example 1 and Example 3 shown in Table 1 were dried in vacuo at 1701C for 4 hours, and molded into a 25 g weight cylindrical, bottomed parison (internal volume: 25 ml) using an injection molding machine maintained at 2751C in cylinder temperature. Each of these parisons was left for 5 minutes at an ambient temperature of 11 01C, and biaxially stretched to obtain a bottle of 350 ml in internal volume (wall thickness: about 1 mm). A bottle 20 obtained from the polymer of Example 1 was superior to a bottle obtained from the polymer of Comparative Example 1 in transparency.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

Claims

1. A modified polyethylene terephthalate molding material containing terephthalic acid as a major dicarboxylic acid component and ethylene glycol as a major glycol component, which contains 0.1 to 15 mol%, based on the total amount of said glycol component present, of 2-methyl-1,3propanediol as part of said glycol component.

2. The modified polyethylene terephthalate molding material according to Claim 1, wherein an 4 GB 2 109 804 A 4 amount of the terephthalic acid is 80 mol% or more based on the total amount of the dicarboxylic acid component present.

3. The modified polyethylene terephthalate molding material according to Claim 1, wherein an amount of the ethylene glycol is 70 mol% or more based on the total amount of the glycol component present.

4. The modified polyethylene terephthalate molding material according to Claim 1, wherein an intrinsic viscosity of the polyethylene terephthalate is 0.4 or more.

5. The modified polyethylene terephthalate molding material according to Claim 1, further containing a polybasic aliphatic carboxylic acid having from 3 to 30 carbon atoms and/or a polybasic 10 aromatic carboxylic acid having from 8 to 30 carbon atoms.

6. The modified polyethylene terephthalate molding material according to Claim 1, further containing a polyhydric alcohol having from 3 to 30 carbon atoms.

7. A modified polyethylene. terephtha late molding material substantially as hereinbefore described in any one of Examples 1 to 4.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

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